Dewar vessels, also denoted as Dewar flasks, are containers designed to provide a good thermal insulation. On the one hand, Dewar vessels are used as Thermos bottles for keeping beverages hot. On the other hand, Dewar vessels may be employed in laboratories to keep samples cool.
Usually, the samples have to be stored at or near the bottom of the Dewar vessel to provide an optimal cooling and to ensure that the sample is covered by a coolant such as liquid nitrogen. This may complicate the handling of the samples and make a high throughput access difficult.
Furthermore, to prevent ice contamination of the coolant by the water vapour contained in the ambient air Dewars are usually closed by a lid. High throughput sample access then requires opening the Dewar frequently, thus resulting in ice contamination of the coolant.